Electron discharge tube



Sept. 17, 1935. w. E. KUHLE ET AL ELECTRON DI SCHARGE TUBE Filed Sept. 29, 1934 INVENTORS WILHELM EBERHARD KUHLE DIETRICH PRINZ @444 I ATTORNEY Patented Sept. 17, 1935 UNITED STATES PATENT OFFICE I 2,014,809 ELECTRON DISCHARGE TUBE Application September 29, 1934, Serial No. 746,216 In Germany October 7, 1933 2 Claims.

This invention relates to electron discharge tubes, more particularly to improvements in the stem and press and the electrode leads of tubes having a metal envelope.

In conventional tubes the electrode leads are sealed in a glass press which, while a good insulator, is fragile and involves a manufacturing method not particularly suitable where the envelope of the tube is of metal instead of glass.

Another disadvantage of a glass press is that at high frequencies, dielectric losses take place in the glass, which under certain conditions may be serious enough to damage the tube. In the conventional tube wide spacing between the different leads and the metal envelope is required for electrical reasons, but this wide spacing is undesirable when working with short waves.

It is therefore an object of our invention to provide an electron discharge tube having a metal envelope with an improved type of stem and press in which the electrode lead wires are imbedded and which is easily formed and attached with a vacuum tight fit to the envelope of the tube.

In accordance with our invention the electrode lead wires are sealed in a combined stem and press of ceramic material, which because of its properties permits a much more simple manufacturing method than when glass is used as the insulating material for supporting the lead wires.

' The novel features which we believe to be characteristic of our invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure ,1 1 is a longitudinal section of an electron discharge tube made in accordance with our invention and Figure 2 is a longitudinal section, with parts broken away, of a modification of the electron discharge tube shown in Figure 1, and embodying our invention.

In Figure 1, the tubular metal envelope In which is closed at one end and also constitutes the anode or plate of the discharge tube, has positioned within it the cathode II, and the grid I2. The electrode leads l3, l4, 15, are sealed in a ceramic insulating member l6 serving as a combined press and stem by means of intermediate glass coatings or tubes l1, l8, and I9 which provide a hermetic or vacuum tight seal around the lead in wires in the press l6 which serves also as a cover or closure for the open end of the anode envelope Ill. The press It has moulded in it a glass tube 20 (Fig, 1) which is provided for exhausting the tube. It is advisable to protect the exhaust tube or stem 20 from mechanical damage by extending the envelope ID, for example, as shown in Figure 1, beyond the press 16 and filling up the cavity thus formed with an 5 insulating compound l6. When this procedure is followed, the electrode leads are preferably surrounded with insulating sleeves l1, l8, and I9 so that they will not be in direct contact with the cast compound. As an alternative, the press 10 I6 can be provided with an aperture into which the exhaust tube can be inserted, in which case only this recess need be filled with the insulating compound after exhaust.

The sealing between the press l6 and the enve- 15 lope I0 is effected by fitting the press l6 supporting the electrode assembly and having a glass coating or collar 2| around the press into the top end 22 of the envelope which is coned or flared outwardly as is best shown in Figure l 20 and placing this assembly in an annealing furnace operated at a suitably high temperature. The glass collar 2| unites the press and envelope. In the modification shown in Figure 2, the envelope 25 is provided with a shoulder 26, upon 25 which the press 21 rests, instead of a flared portion into which the press fits as in Figure 1. The press 21 may be sealed to the envelope 25 by a glass collar 29.

Especially where small-sized tubes are dealt 30 with, the anode vessel I may be provided with projections or lugs 23 (Fig. 1) whereby the tube may be fitted into a suitable socket bayonet fashion.

In the modification shown in Figure 2 the ex- 35 haust tube 28 is a metal tube and is joined to the metal anode envelope7 25, preferably at the bottom end, instead of a glass tube imbedded in the ceramic insulating press 16 as shown in Figure 1.

According to this invention the insulating mem- 40 her serving as the stem and press consists of ceramic material whose dielectric loss at radio frequency voltages and currents is less than 0.5%. As a result, it is feasible to use tubes of this conr struction for short and even ultra-short waves.

While we have indicated the preferred embodiments of our invention of which we are now aware and have also indicated only one specific application for which our invention may be em- 50 ployed, it will be apparent that our invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of our invention as set forth in the appended claims.

What we claim as new is:-

1. An electron discharge tube having a tubular metal envelope open at one end, an insulating member of ceramic material fitted into the open end of the envelope for closing the open end of the envelope, and providing a cup-shaped cavity between the insulating member and the open end of the envelope, a layer of glass intermediate the wall of the envelope and the insulating member for sealing the member to the envelope with a vacuum tight fit, lead wires imbedded in said insulating member, electrodes supported on said lead wires within the metal envelope, an exhaust tube imbedded in said insulating member with one end extending into said cup-shape cavity, and a compound for filling the cavity around the lead wires and said exhaust tube for protecting the end of said exhaust tube.

2. An electron discharge tube having a tubular metal envelope open at one end, an insulating member of ceramic material for closing the open end of said envelope and providing a cup-shaped cavity between the insulating member and the open end of the envelope, a layer of glass intermediate the wall of said envelope and the insulating member for sealing the member to the envelope with a vacuum tight fit, lead wires imbedded in the insulating member, a layer of glass intermediate the lead wires and the insulating member to provide a vacuum tight seal, electrodes supported on said lead wires within the metal envelope, an exhaust tube embedded in said insulating member with one end extending into said cup-shaped cavity and a compound for filling the cavity around the lead wires in said 15 exhaust tube for protecting said exhaust tube and lugs extending from the sides or the envelope near one end and adapted to be received in a socket for holding the tube.

WILHELM EBERHARD KUHLE. DIETRICH PRINZ. 

